Accessory Nerve Root and Associated Dural Injury
Incidences Encountered During Lumbar Microdiscectomy
Lomber Mikrodiskektomi Esnasında Rastlanan Aksesuar Sinir Kökü ve Dural Yaralanma Sıklığı
Șeyho Cem Yücetaș1, Can Hakan Yıldırım1, Mehmet Bülent Balioğlu2, Yusuf Ehi3, Ahmet Faruk Soran4, Aytaç Akbașak1
1Department of Neurosurgery, Kafk as University Faculty of Medicine, Kars, Turkey; 2Baltalimanı Education and Research Hospital, İstanbul, Turkey; 3Department of Neurology, Kafk as University Faculty of Medicine, Kars, Turkey; 4Department of Neurosurgery, Harran University Faculty of Medicine, Şanlıurfa, Turkey
Yard. Doç. Dr. Şeyho Cem Yücetaş, Kafk as Üniversitesi 36100 Kars, Türkiye, Tel. 0 474 225 21 06 Email. seyhocem@hotmail.com
Geliş Tarihi: 22.01.2014 • Kabul Tarihi: 19.03.2014 ABSTRACT
AIM: We aimed to fi nd the incidence of accessory nerve roots and their respective sites encountered intraoperatively during lumbar microdiscectomy operations, and to draw attention to the fi ndings associated with the presence of accessory nerve roots.
METHODS: This study was conducted by retrospective analysis of the records of patients (N=820) who were operated by the method of microdiscectomy in three medical centers between April 2010 and August 2013. Cases that indicated surgery upon neurological and radiological examinations were included in the study. In the study, accessory nerve root abnormalities and the related dural tears or nerve root injuries were assessed.
The variables of sex, presence of accessory roots and dural injury were used as independent variables to analyze the other variables.
RESULTS: Accessory nerve root anomaly was detected in 22 (3%) of 820 operated patients. L4-5 was the most frequent level for her- nia formation and followed by L5-S1 level. The hernia side, as right or left, did not signifi cantly differ at any level (p>0.05).
L5-S1 space was the most frequent site for accessory nerve roots and followed by L4-5 space. However, the frequency of right or left side location of the accessory nerve roots were not different at any lumbar disc level (p>0.05).
The presence of an accessory nerve root increased the chance of dural tear injury. Female gender, independent from the presence of an accessory nerve root, was a risk factor for dural tear injury.
CONCLUSION: The accessory nerve root is most frequently observed at the L5-S1 disc level and its presence increases the chance of dural injury. In addition, female gender is an indepen- dent risk factor for dural injury.
Key words: accessory nerve root; dural tear; lumbar disc herniation;
microdiscectomy
ÖZET
AMAÇ: Çalıșmadaki amacımız lomber mikrodiskektomi girișimleri sırasında intraoperatif olarak karșılașılan aksesuar sinir kökü görül- me ve yerleșim yeri sıklığı sonuçlarımızı sunmak ve aksesuar root varlığına ilișkin bulgulara dikkat çekmektir.
YÖNTEM: Bu çalıșma Nisan 2010 ile Ağustos 2013 tarihleri ara- sında mikrodisektomi yöntemiyle opere olan, üç merkezdeki hasta- ların (N=820) kayıtlarının retrospektif olarak incelenmesiyle yapıldı.
Çalıșmaya nörolojik ve radyolojik muayeneler sonucu operasyon endikasyonu konulan olgular dahil edildi. Çalıșmada aksesuar sinir kökü anomalisi ve buna bağlı dura veya sinir kökü yaralanma oran- ları incelendi.
Cinsiyet, aksesuar sinir kökü ve dura yaralanması varlığı, diğer değiș- kenleri incelemek üzere bağımsız değișkenler olarak kullanıldı.
BULGULAR: Lomber aksesuar sinir kökü anomalisi opere edilen 820 hastanın 22’sinde (%3) tespit edildi. L4-5 disk hernisi formas- yonunda en çok rastlanan seviye olup, ikincisi ise L5-S1 seviye- siydi. Disk hernisinin sağ ya da sol tarafta olması, hiçbir seviyede dikkate değer bir farklılık olușturmamıștır (p>0,05).
Aksesuar sinir köklerinin en sık rastlanıldığı yerleșim yeri L5-S1 boșluğu olmuștur ve ikinci olarak L4-5 gelmektedir. Ancak aksesu- ar sinir köklerinin sağ ya da sol tarafta yerleșim sıklığı, hiçbir lomber disk seviyesinde farklı olmamıștır (p>0,05).
Aksesuar sinir kökü varlığı, dura yaralanması ihtimalini arttırmıștır.
Aksesuar sinir kökü varlığından bağımsız olarak cinsiyetin kadın ol- ması, dura yaralanmalarında bir risk faktörü olmuștur.
SONUÇ: Aksesuar sinir kökü en sık L5-S1 disk aralığındadır.
Aksesuar kökün varlığı, dura yaralanması ihtimalini arttırmaktadır.
Ayrıca cinsiyetin kadın olması, dura yaralanmaları için bağımsız bir risk faktörüdür.
Anahtar kelimeler: aksesuar sinir kökü; dura yırtılması; lomber disk hernisi;
mikrodiskektomi
Introduction
Disc herniation is the general name given to the medi- cal condition presenting itself as a pathology that dis- torts the shape and content of the discus interverte- bralis due to reasons other than infection or tumor1. Lumbar disc herniation is most frequently observed in the L4-5 level. Currently, surgical therapy is typically carried out by microdiscectomy; however many other surgical methods are also used2,3.
Although it is rare, the accessory nerve roots may be encountered intraoperatively during lumbar disc sur- gery and they are hardly defi ned before surgery by us- ing magnetic resonance imaging (MRI) and computer- ized tomography (CT) modalities4.
Lumbosacral nerve root abnormalities are classifi ed under fi ve or six groups5. Awareness of an accessory nerve root abnormality reduces intraoperative injuries6. During surgery, certain complications may develop such as dural tear, nerve root injury and vascular injuries which are mostly due to anatomical variations or intra- operative diffi culties of the exploration of the surgical fi eld1,7. Th e demonstration of a conjoined nerve root ab- normality within the operation fi eld during lumbar mi- crodiscectomy reduces dural tears or nerve root injuries4. In this study, we aimed to fi nd the incidence of acces- sory nerve roots and their respective sites encountered intraoperatively during lumbar microdiscectomy oper- ations, and to draw attention to the fi ndings associated with the presence of accessory nerve roots.
Methods
Th is retrospective study was conducted by the exami- nation of the records of patients who underwent sur- gery in the brain and nerve surgery clinics of the Kafk as University School of Medicine, Harran University School of Medicine and the Adıyaman Training and Research Hospital. Before the examination of the fi les, the local medical ethics committees approved the study and the necessary approvals were also obtained from related institutions.
Th e population of the study consisted of patients indi- cated with operation as a result of neurological and ra- diological examinations. For sampling, the data of 820 patients who underwent microdiscectomy due to lum- bar herniation between April 2010 and August 2013 in the three hospitals were used.
Patients with previous multiple operations at the same level, total or unilateral partial laminectomy, scoliosis
or congenital vertebral abnormality were excluded.
Discectomies secondary to trauma were also excluded.
All patients had had MRI examinations preoperatively and some of them had had additional CT imaging ex- amination whereas it had been necessary. All patients’
extruded or sequestered discs had been detected pre- operatively by using MRI or CT imaging (Figures 1,2).
Study variables included demographics of the partici- pants, the existence of accessory nerve root detected during microdiscectomy (Figure 3), the level and side of the accessory nerve root and the complication of du- ral tear.
Statistical analysis was performed by using SPSS 21.0 package program for windows (Chicago, USA).
Constant variables were shown as mean±standard de- viation whereas categorical variables were shown with median values. Th e incidences of accessory root and their locations, and the development of dural tear were evaluated using Chi-square test. Gender, presence/
absence of accessory nerve root and presence/absence of dural injury were used as independent variables to analyze the other variables. Variables with normal and non-normal distribution were compared with in- dependent samples of Student t and Mann Whitney tests, respectively. Correlation analysis among variables was performed by using Pearson’s correlation test. A p value of <0.05 was considered signifi cant.
Results
A total of 820 discectomy cases were evaluated. Of the included patients 440 and 380 were females and males, respectively. Th e youngest patient was 19 years old whereas the oldest one was 65 years old; the mean age of the patients was 42.6 years.
Lomber disc hernia localization levels were classifi ed according to the intervertebral disc spaces as: L1-2, L2-3, L3-4, L4-5 and L5-S1 (Table 1). L4-5 was the most frequent level for hernia formation and followed by L5-S1 level. Th e hernia side, as right or left , did not signifi cantly diff er at any level (p>0.05).
L5-S1 space was the most frequent site for accessory nerve roots and followed by L4-5 space (Table 2).
However, the frequencies of right or left side location of the accessory nerve roots were not diff erent at any lumbar disc level (p>0.05).
All patients had preoperative motor and sensory loss.
Lower leg was involved in four patients with conjoined nerve and in 15 patients without conjoined nerve.
Urinary incontinence was observed in three of the pa- tients who had an accessory nerve root and in 13 of the patients, who did not. Cauda equina fi ndings were ob- served in fi ve patients, who did not have accessory nerve root and in one patient with an accessory nerve root.
Female and male patients were compared by using the variables of age, lumbar hernia level, left and right sid- ed hernia, presence of accessory nerve root and occur- rence of dural tear injury (Table 3). Dural tear injury was signifi cantly higher in female patients (p<0.05),
Figure 2. T2A axial MRI. L5-S1 lumbar disc herniation.
Figure 1. T2A sagittal MRI. L5-S1 lumbar disc herniation.
Figure 3. Intraoperative view of the accessory nerves.
Table 1. Distribution of operated disc hernias at the lumbar region
Lumbar disc level
Right sided (n=413) Left sided (n=407)
n % n % p*
L1-2 3 0.7 4 0.9 0.705
L2-3 12 3 8 2 0.371
L3-4 28 7 26 6 0.785
L4-5 222 53.7 197 48.4 0.222
L5-S1 148 36 172 42.3 0.180
*X2 test
Table 2. Distribution of accessory nerve roots at the lumbar region
Lumbar disc level
Right sided (n=13) Left sided (n=9)
n % n % p value*
L1-2 0 0 0 0 n/a
L2-3 0 0 0 0 n/a
L3-4 1 8 0 0 0.335
L4-5 2 15 3 33 0.559
L5-S1 10 77 6 77 0.182
*Mann Whitney Test
Table 3. Comparison of study findings according to the independent variables of gender, presence of accessory nerve root and presence of dural injury
Female patients (n=440) Male patients (n=380) p value
Age, year 42.7 ± 12.6 42.5 ± 13.5 0.888*
Hernia disc level L4-5 L4-5 0.873**
Right side hernia, % 48 53 0.228**
Left side hernia, % 52 47 0.228**
Accessory root, % 3 2 0.605**
Dural injury, % 6 2 0.018**
Accessory nerve root present (n=22) Accessory nerve root absent (n=798)
Female patients, % 59 54 0.605**
Male patients, % 41 46 0.605**
Age, year 44.5 ± 12.2 42.6 ± 12.9 0.489*
Hernia disc level L5-S1 L4-5 0.002**
Right side hernia, % 59 50 0.407**
Left side hernia, % 41 50 0.407**
Dural injury, % 27 4 <0.001**
Dural injury occured (n=34) Dural injury did not ocur (n=786)
Female patients, % 74 43 0.012*
Male patients, % 26 47 0.012*
Age, year 41.4 ± 12.6 42.7 ± 12.9 0.577*
Hernia disc level L4-5 L4-5 0.472**
Right side hernia, % 56 50 0.511**
Left side hernia, % 44 50 0.511**
Accessory root, % 18 2 <0.001**
*Independent samples Student t test, **Mann Whitney test
retrospective study and some variables could not be analyzed. For example, the lack of variables of patients’
height and weight kept us from analyzing the diff er- ences between female and male patients. Probably the shorter female patients had narrower intervetebral disc spaces, which made the surgical exposure harder. Th us, it is hard to demonstrate whether the higher injury rate resulted from the female gender or narrower interver- tebral disc spaces.
Comparison with previous studies
Lumbar disc herniation was defi ned by Mixer and Barr in 1934. In their lifetime, about 80% of the adult pop- ulation experiences an episode of backaches that aff ect their functionality and some of these episodes are re- lated to disc conditions1,8.
Many methods are used in the diagnosis of lumbar disc herniation, but currently, the mostly preferred methods are MRI and CT imaging4,9,10.Lumbar disc herniation typically develops in L4-5 and L5-S1 lev- els and in less than 5% of the instances, it develops in other regions11. In our patients, the distribution of sites was similar, in that approximately 90% developed in L4-5 and L5-S1 levels. Patients may present with radicular pain, motor and sensory loss, refl ex changes, urinary and fecal incontinence and cauda equina syn- drome fi ndings8,12. In all patients we operated, there was motor and sensory loss. Th e lower part of the leg was involved in 4 cases with an accessory nerve root and in 15 cases without an accessory nerve. Urinary incontinence was detected in six patients and three of them had conjoined nerve root. Cauda equina fi nd- ings were detected in one case with accessory nerve root whereas in fi ve cases without. Motor and sensory examinations were conducted in all patients preoper- atively8. In our study, we examined all patients with a preoperative Lasègue test and a femoral nerve crossed straight-leg-raise test.
In lumbar disc herniations, treatment is classifi ed under two headings, namely conservative and surgical meth- ods13,14. Various surgical methods are employed in lum- bar disc herniations1. We opearated all of our patients by using the conventional microdiscectomy method.
During this kind of surgery, nerve root abnormali- ties may be encountered15. Some authors separated ac- cessory nerve root abnormalities into three, fi ve or six groups5,6. Th e most commonly used is the Neidre and MacNab classifi cation. Lumbosacral nerve root abnor- malities were observed in 46 patients out of a total of however other variables did not diff er signifi cantly
between female and male patients (p>0.05).
Th e patients with or without an accessory nerve root were compared with each other by using the variables of gender, age, lumbar hernia level, left and right sid- ed hernia, and occurrence of dural tear injury (Table 3). Lumbar hernia level was signifi cantly lower in patients with an accessory nerve root in comparison with the patients without an accessory nerve root (p<0.05). However, other variables were not aff ected by the presence or absence of an accessory nerve root (p>0.05).
Operations complicated with a dural tear injury were compared with operations without a complication by using the variables of gender, age, lumbar hernia level, left and right sided hernia, and presence of an acces- sory nerve root (Table 3). Dural tear injury was signifi - cantly higher in female patients and in patients with an accessory nerve root (p<0.05). However; age, lumbar hernia level and side did not diff er in operations com- plicated or not with a dural tear injury (p>0.05).
Correlation analysis showed that the chance of pres- ence of an accessory nerve increased in lower lumbar hernias and presence of an accessory nerve root in- creased the chance of a dural injury (p<0.05).
Discussion Principal fi ndings
Our study fi ndings suggested that accessory nerve roots were encountered in lower level lumbar hernias, particularly the hernias involving L4-5 and L5-S1.
Th e presence of an accessory nerve root increased the chance of dural tear injury and female gender indepen- dent from the presence of an accessory nerve root was a risk factor for dural tear injury.
Strengths and limitations
To our knowledge, this is the fi rst study including such a large sample of 820 patients. In addition, our study population included patients from three diff erent centers located in diff erent cities. Although, the study population included only the symptomatic patients, the relation of the presence of an accessory nerve root and intraoperative dural injury is also important in this population.
Although our study included 820 operations per- formed with microdiscectomy technique, it was a
4. Trimba R, Spivak JM, Bendo JA. Conjoined nerve roots of the lumbar spine. Spine J 2012;12:515–24.
5. Postacchini F, Urso S, Ferro L. Lumbosasacral nerve-root anomalies. J Bone Joint Surg Am 1982;64:721–3.
6. Burke SM, Safain MG, Kryzanski J, et al. Nerve root anomalies:
implications for transforaminal lumbar interbody fusion surgery and a review of the Neidre and Macnab classifi cation system.
Neurosurg Focus 2013;35:9–13.
7. Leung PC. Complications in the fi rst 40 cases of microdiscectomy.
J Spinal Disord 1988;1:306–10.
8. Toplamoğlu H. Lumber Disc Hernia. In: Akson K, Pamir N, editörler. Temel nöroşirürji. Ankara: Hacettepe yayınları;
2005:1056–61.
9. Kubaszewski Ł, Nowakowski A, Gasik R, et al. Intraobserver and interobserver reproducibility of the novel transcription method for selection of potential nerve root compression in MRI study in degenerative disease of the lumbar spine. Med Sci Monit 2013;19:216–21.
10. Imaad-ur-Rehman, Hamid RS, Akhtar W, et al. Observer variation in MRI evaluation of patients with suspected lumbar disc herniation and nerve root compression: comparison of neuroradiologist and neurosurgeon’s interpretations. J Pak Med Assoc 2012;62:826–9.
11. Raja RA, Khemani VD, Lakhair MA, et al. Discectomy in single level lumbar disc disease. J Ayub Med Coll Abbottabad 2012;24:81–3.
12. Biluts H, Munie T, Abebe M. Review of lumbar disc diseases at Tikur Anbessa Hospital. Ethiop Med J 2012;50:57–65.
13. Deburge A, Bex M, Lassale B, et al. Surgical technic in the treatment of stenosis of the lumbar canal. Acta Orthop Belg 1987;53:412–9.
14. Durakan A, Tatlısumak T. Kemik ve eklem hastalıkları ile ilişkili Nörolojik bozukluklar. In: Bahar SZ, Çoban O, editors. Neurology and General Medicine. Ankara:Güneş Tıp Kitapevleri; 2010: 441–8.
15. McCulloch JA, Waddell G. Variation of the lumbosacral myotomes with bony segmental anomalies. J Bone Joint Surg Br 1980;62:475–80.
16. Scuderi GJ, Vaccaro AR, Brusovanik GV, et al. Conjoined lumbar nerve roots: a frequently underappreciated congenital abnormality. J Spinal Disord Tech 2004;17:86–93.
17. Taghipour M, Razmkon A, Hosseini K. Conjoined lumbosacral nerve roots: analysis of cases diagnosed intraoperatively. J Spinal Disord Tech 2009;22:413–6.
18. Proietti L, Scaramuzzo L, Schiro GR, et al. Complications in lumbar spine surgery: A retrospective analysis. Indian J Orthop 2013;47:340–5.
19. Yoshihara H, Yoneoka D. Incidental dural tear in lumbar spinal decompression and discectomy: analysis of a nationwide database. Arch Orthop Trauma Surg 2013;15:20–3.
2123 patients in the study conducted by Posthaccini et al., and these abnormalities were divided into fi ve class- es5. According to the Neidre and MacNab classifi cation, nerve root abnormalities were divided into six groups6. Berta et al. detected conjoined nerve root abnormalities in four out of 80 patients16. In the study conducted by Taghipour et al., conjoined nerve root abnormality was most frequently observed in L4–5 level17. In our study, conjoined nerve root abnormality was detected in 22 out of 820 patients and mostly in L5-S1 level with 16 patients.
Although microdiscectomy is the best surgical method, complications at a rate of 2–14% have been reported.
Th ese complications include instability of spinal liga- ments and spinal muscles during laminectomy, facet deformation, spinal dural tears and root injuries18,19. In a study conducted by Leunge, dural tears were detect- ed in two patients out of a total of 40 patients7. In our study, dural injury or dural tear were experienced in 28 patients (3.41%) with no accessory nerve root and in 6 patients (27.27%) with accessory nerve root. Th ese were treated using appropriate methods. Th e rate of dural tear or root injury during surgery was found to be higher and more signifi cant in patients with an ac- cessory nerve root.
As a conclusion, during lumbar microdiscectomy op- erations, accessory nerve roots were most frequently observed at the lower segments including L4-5 and L5-S1 levels, and the dural tears and nerve root inju- ries were higher than the normal group. Accordingly, we wish to emphasize that during lower segment disc herniation operations, special attention to the acces- sory nerve root will be useful in preventing dural tears and root injuries.
References
1. Akbay A, Bozkurt G, Palaoğlu S. Disk hernileri ve spinal dar kanal. In: Akson K, Pamir N, editors. Temel Nöroşirürji.
Ankara: Hacettepe yayınları; 2004:277–93.
2. Veresciagina K, Spakauskas B, Ambrozaitis KV. Clinical outcomes of patients with lumbar disc herniation, selected for one-level open-discectomy and microdiscectomy. Eur Spine J 2010;19:1450–8.
3. Blamoutier A. Surgical discectomy for lumbar disc herniation:
surgical techniques. Orthop Traumatol Surg Res 2013;99:187–96.
